Solid oxide fuel cells are temperature dependent electrochemical devices. The operational temperature of the fuel cell affects the rate of the electrochemical reaction and electrical (ionic) resistance of the cells. To this end one of the main requirements of a fuel cell system is to control the temperature of the anode and cathode gas streams to the fuel cells to optimise the operating temperature of the fuel cells and hence the operating point of the fuel cells across the power output range. The result of good optimisation is higher fuel cell system efficiency. For this purpose it is desirable to measure the temperature of gases flowing at various measurement points within an apparatus comprising the fuel cell. Such temperature measurement may be in the fuel cell stack or the fluid conduits to and or from the fuel cells or the fuel cell stack. Such gas flow is, however, often turbulent and at varying flow speeds that may not be precisely known. Moreover, physical sensors that can be used in an economically feasible way for making such measurements either lack a desired measurement accuracy or have to be protected from the environmental conditions presented to them by the gas flow to avoid deterioration. Sheltering such sensors, however, can give rise to further inaccuracies in conducted measurements particularly where the measurements occur in confined conduits. The present invention seeks to address, overcome or mitigate at least one of these or other disadvantages.